It is desirable to inject and distribute various fluids to the multifilament filter tow used in the manufacture of tobacco smoke filters. These fluids, which are injected and distributed to the tow alone or in combination with liquid or gaseous carriers, may be flavorants, tow blooming agents, lubricants, sizing solutions, finish compositions, plasticizers, or the like, and are intended to impart desired physical or flavor characteristics to the fluid-treated tow.
Tobacco smoke filters are typically manufactured from cellulose acetate filaments which are formed into a multifilament rope or tow. The tow is treated with various consolidating additives and compressed or condensed into a continuous filter rod and, subsequently, is cut to a desired length. As is well known in the art, the cut filter rod is then assembled in coaxial relationship with a suitable cut section of a rod of tobacco filler. The assembly is then wrapped with a suitable paper or fiber wrapping to form a complete smokable product in the form of, for example, a cigarette, cigarillo, or cigar.
The addition of one or more additives to the tobacco smoke filter, such as flavorants and the like, enhances the flavor or other characteristics of the smoke as it is drawn therethrough by the user. One method of maximizing this enhancement is by selectively distributing the additive through the filter tow such that the additive is distributed at a predetermined location relative to the longitudinal axis of the tow. In general, it is desirable to uniformly distribute the additive along the central or longitudinal axis of the filter tow. Uneven or eccentric distribution of a flavorant additive can result in an inconsistent and undesirable tobacco smoke taste.
Various approaches have been used to distribute additives in a continuous multifilament filter tow. U.S. Pat. No. 4,549,875, assigned to the assignee of this invention, discloses one such approach and the disclosure thereof is incorporated herein by reference. In that patent, a conventional rod-making apparatus is disclosed which has been modified for injecting an additive into the filter tow in a tongue device located downstream of a converging horn. A conduit mounted in cantilevered fashion to the horn extends into the tongue device and terminates in a nozzle disposed coaxially in the filter tow path. An additive flowed under pressure into the conduit is distributed through a plurality of orifices disposed in the nozzle.
Because the cantilevered conduit and nozzle extend a significant distance from the converging horn mounting into the filter tow path, it is sometimes difficult to initially position the nozzle coaxially on the tow path axis and to precisely maintain the nozzle in that position because of forces created by the advancing filter tow as it passes around the conduit and nozzle. A minor deviation in the position of the conduit at its mounting point on the horn may result in a major deviation of the nozzle relative to the longitudinal axis of the advancing tow. Such deviation will result in asymmetric and inconsistent additive distribution to the filter tow.
Variations in the speed and supply volume of the filter tow as well as machine vibration may also adversely affect the positional stability of the cantilevered conduit and nozzle. Given these conditions, the conduit and nozzle must be frequently checked for proper positioning and repositioned in a trial-and-error fashion, resulting in considerable production down time, as well as uncertainty that the additive is properly distributed in the finished product, especially in the usual case where the additive is a colorless liquid. Furthermore, the nozzle must be repositioned for each filter tow run, especially when successive tow runs are of different tow composition, density, cross-section, or speed.
U.S. Pat. Nos. 4,476,807 and 4,850,301, also assigned to the assignee of this invention, disclose other apparatus for applying an additive to a filter tow upstream of the rod-forming converging horn and tongue device of the filter making machine. In U.S. Pat. No. 4,476,807, for example, the additive is introduced into the tow in the filter tow blooming jet apparatus and in U.S. Pat. No. 4,476,807, a plasticizer additive is introduced to a thin flattened band of tow by a perforated roll applicator disposed upstream of the blooming jet apparatus. While such apparatus are very effective for distributing an additive, such as a plasticizer, uniformly throughout the filter tow, they are not as effective in concentrating an additive along the axis of the finished filter rod as is particularly desirable in the case of a flavorant additive.
It is also known to inject a gaseous fluid, such as air, into a tow as it travels through a converging and consolidating tongue device for the purpose of slightly blooming the tow and thereby reducing the total volume of tow necessary to manufacture a given length of filter rod product. It will be appreciated that even a small reduction in the total volume of tow used in the manufacture of a given number of filter cigarettes, will amount to substantial savings in manufacturing costs for those cigarettes. In the known construction, air is injected from a manifold through a series of holes formed in the upper portion of the converging wall of the tongue device. It has been found, however, that this construction is not particularly effective in blooming the tow and is clearly incapable of injecting an additive along the longitudinal axis of the tow.
In view of the foregoing, it would be desirable to provide an apparatus for injecting a fluid, including gases, liquids and combinations thereof, into a multifilament filter tow which is not subject to the positioning difficulties and other limitations of the prior art devices. Such an apparatus would be particularly useful for the purpose of concentrating an additive precisely along the longitudinal axis of the tow or for effectively providing additional blooming of a filter tow to reduce the total volume of tow used in filter cigarette manufacture.